JP4108806B2 - Combustion chamber structure of in-cylinder direct injection spark ignition engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a combustion chamber structure of an in-cylinder direct injection spark ignition engine, and in particular, a structure of a cylinder head and a piston for generating a tumble flow, and an ignition plug for optimizing the combustion of fuel sprayed from an injector. This relates to the placement of the injector.
[0002]
[Prior art]
Generally, in this type of in-cylinder direct injection spark ignition engine, it is possible to selectively switch between two combustion methods, stratified combustion and uniform combustion. Stratified combustion is achieved by stratifying in the second half of the compression stroke and forming a combustible mixture around the spark plug, and uniform combustion is achieved by mixing fuel injected during the intake stroke with intake air. .
[0003]
As an example of such a combustion chamber structure suitable for stratified combustion and uniform combustion, the applicant of the present invention disclosed in Japanese Patent Laid-Open No. 6-42352 that the injector is disposed vertically in the center of the top of the combustion chamber. A piston with a cavity formed on the top surface of the piston facing the injection direction of the injector was proposed. Furthermore, in the present invention, the electrode of the spark plug faces the vicinity of the injection hole of the injector.
[0004]
According to this combustion chamber structure, at the time of stratified combustion, the rear end of the fuel spray that has been injected just before the ignition timing is ignited by the ignition plug, or the air-fuel mixture reflected by colliding with the piston cavity is ignited, thereby stabilizing Try to get burning. Moreover, at the time of uniform combustion, a uniform air-fuel mixture can be obtained by starting injection at a relatively early stage of the intake stroke. In addition, according to this combustion chamber, the fuel spray does not adhere to the wall surface of the cylinder bore because the injector is disposed vertically on the top of the combustion chamber, so that deterioration of combustion due to so-called fuel cooling is prevented. Can do.
[0005]
[Problems to be solved by the invention]
By the way, when a combustible air-fuel mixture is formed at the ignition position of the spark plug and stable combustion is to be performed, the optimal fuel injection end timing (BITI) for ignition has a characteristic as shown by a broken line in FIG. . As understood from this characteristic diagram, it is understood that the dependence of the optimal fuel injection timing on the fuel injection amount (engine load) is low, that is, it is only necessary to keep the injection end timing substantially constant with respect to the ignition timing. .
[0006]
However, as shown in FIG. 14, when the fuel injection (end) timing is advanced (accelerated) with respect to the ignition timing, the premixing of the injected fuel and air is promoted, so the HC and NOx emissions are increased by a predetermined amount. It increases to the angle value and then gradually decreases. Conversely, if the fuel injection timing is retarded (retarded) with respect to the ignition timing, the droplets of injected fuel burn, and so the amount of soot increases due to insufficient vaporization of the fuel. It should be noted that the generation time of this soot tends to occur at an earlier injection timing as the fuel injection amount increases. Therefore, in the optimal injection timing (BITE) control, it is necessary to advance the injection timing as the fuel injection amount (engine load) increases from the viewpoint of measures against exhaust gases (soot, CO, HC, NOx, etc.).
[0007]
As a result, in the stratified combustion, the control range is inevitably different between the BITI control that focuses on ignitability and the BITE control that focuses on exhaust gas countermeasures.
[0008]
However, in the combustion chamber structure in which the flat cavity 1a is formed on the top surface of the piston as shown in FIG. 15, for example, when the fuel injection (end) timing is set to the advance side, the fuel is injected from the injector 2. The fuel spray collides with the cavity 1a and is diffused around. As a result, the fuel spray does not reach the vicinity of the electrode 3a of the spark plug 3, and a combustible air-fuel mixture cannot be formed around the electrode 3a, resulting in misfire or poor combustion. Therefore, in such a piston-shaped engine, it is necessary to end the injection near the ignition timing and ignite the rear end of the fuel spray. However, there is a limit to advance the fuel injection (end) timing according to the fuel injection amount.
[0009]
In order to solve this problem, it is conceivable to change the flat cavity 1a on the top surface of the piston into a curved surface so as to wind up the fuel injected from the injector along the curved surface of the cavity. According to this concept, it becomes possible to form a combustible air-fuel mixture around the electrode of the spark plug, and the fuel injection timing can be set freely to some extent. However, according to this method that relies on the fuel injection shape, when the fuel injection timing is further advanced, the combustible air-fuel mixture is not sufficiently formed around the spark plug.
[0010]
In general, in the case of stratified combustion, as the average air-fuel ratio approaches the stoichiometric air-fuel ratio, that is, as the fuel injection amount increases, the air-fuel mixture around the spark plug electrode becomes excessively concentrated or insufficiently vaporized. , CO, HC, etc. are likely to occur. Therefore, the average air-fuel ratio at the time of stratified combustion has a certain rich limit. On the other hand, even with uniform combustion, the entire air-fuel mixture is uniformly mixed, so there is a lean limit that cannot be ignited.
[0011]
It is known that stratified combustion is suitable for low and medium load operation, while uniform combustion is suitable for high load operation. The engine load changes continuously during traveling. Further, in the cylinder injection engine, the air-fuel ratio is variably set according to the engine load. Therefore, if the rich limit at the time of stratified combustion is leaner than the lean limit at the time of uniform combustion, the air-fuel ratio changes intermittently every time the engine operating range changes, that is, the operating range is uniform from stratified combustion. When switching to combustion, the air-fuel ratio changes instantaneously in the rich direction, and when switching from uniform combustion to stratified combustion, the air-fuel ratio changes instantaneously in the lean direction.
[0012]
Thus, in a situation where the air-fuel ratio changes intermittently every time the combustion system is switched, exhaust emission deteriorates and good drivability cannot be obtained. This situation is as shown in FIG.
[0013]
In order to maintain the continuity of the air-fuel ratio (when the intake air amount is constant), if the fuel injection amount at the time of stratified combustion is set to the same level P1 as the fuel injection amount of the lean limit P3 at the time of uniform combustion, generation of soot, Inconvenience such as CO increase occurs. On the other hand, if the fuel injection amount is set to the rich limit P2 that avoids such inconvenience when the combustion system is switched from stratified combustion to uniform combustion, the fuel injection amount suddenly increases from P2 to P3, and the engine load increases. The continuity of engine output with respect to will not be maintained.
[0014]
On the other hand, in consideration of expanding stratified combustion to a high load region in order to further improve fuel consumption and exhaust emission, it is necessary to advance the fuel injection timing to the beginning of the compression stroke. In this case, the fuel spray is diffused, and a part of the fuel spills out of the piston cavity to become a flame extinguishing layer, not only increasing the amount of unburned HC, but also the fuel adhering to the cylinder liner liquefies and causes oil dilution. .
[0015]
The present invention is intended to avoid the disadvantages of these conventional examples.
An object of the present invention is to provide an in-cylinder direct-injection spark ignition engine that can set a wide range of injection end timings during stratified combustion in accordance with the fuel injection amount without incurring emission deterioration, and can always obtain stable ignition performance. It is to provide a combustion chamber structure.
[0016]
A further object of the present invention is to provide a combustion chamber structure of a direct injection type spark ignition engine capable of ensuring good drivability by ensuring continuity of the engine load when switching from stratified combustion to uniform combustion. That is.
[0017]
Another object of the present invention is to provide a combustion chamber structure for an in-cylinder direct injection spark ignition engine that can expand stratified combustion to a high load region and further improve fuel efficiency and exhaust emission.
[0018]
[Means for Solving the Problems]
The combustion chamber structure of the first in-cylinder direct injection spark ignition engine according to the present invention is:
Between the intake port and the exhaust port opened in the roof of the combustion chamber, an injector inclined by a first inclination angle toward the exhaust port side with respect to the axis of the cylinder is disposed,
Inclined to the exhaust port side roof or arranged in parallel with the exhaust port side roof so that the intake port forms an intake tumble flow along the exhaust port side roof,
A curved piston cavity is formed on the top surface of the piston to reflect the fuel spray injected from the injector along with the intake tumble flow toward the roof on the intake port side,
A spark plug is arranged on the roof on the intake port side,
The electrode of the spark plug is located near the injection hole of the injector and faces the outflow position of the fuel spray reflected by the intake tumble flow and the piston cavity.
[0019]
The combustion chamber structure of the second in-cylinder direct injection spark ignition engine according to the present invention is:
In the combustion chamber structure of an in-cylinder direct injection spark ignition engine that generates a tumble flow in the intake air supplied through the intake port that opens to the roof of the combustion chamber,
Between the intake port and the exhaust port opened in the roof of the combustion chamber, an injector inclined by a first inclination angle toward the exhaust port side with respect to the axis of the cylinder is disposed,
The intake port is inclined by a second inclination angle relative to the cylinder axis so that the intake air directly collides with the piston to form an intake tumble flow;
A curved piston cavity is formed on the top surface of the piston to reflect the fuel spray injected from the injector along with the intake tumble flow toward the exhaust port side roof,
A spark plug is arranged on the roof on the intake port side,
The electrode of the spark plug is located near the injection hole of the injector and faces the outflow position of the fuel spray reflected by the intake tumble flow and the piston cavity.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 to FIG. 7 show examples of combustion chambers of an in-cylinder direct injection spark ignition engine. This example shows the combustion chamber of a 4-valve DOHC engine. In these drawings, reference numeral 11 denotes a cylinder, reference numeral 12 denotes a cylinder head, reference numeral 13 denotes a piston, and reference numeral 14 denotes a top surface 13 a of the piston 13 located at the top dead center, an inner wall of the cylinder 11, and a bottom surface of the cylinder head 12. The combustion chamber formed is shown.
[0021]
An inner surface recess 12 a is formed on the bottom surface of the cylinder head 12. In this embodiment, the inner surface recess 12a has a pent roof shape. A top portion 12b of the inner surface recess 12a is formed slightly spaced from the center of the cylinder (line A). The injector 15 is disposed in the vicinity of the center of the top portion 12b with the injection hole 15a facing the combustion chamber. An intake port 16 is provided on each side of the inner surface recess 12a sandwiching the injector 15 of the intake side pent roof 12c, and an exhaust port 17 is provided on each side of the inner surface recess 12a sandwiching the injector 15 of the exhaust side pent roof 12d. Further, a squish area 18 is formed on the bottom surfaces of the pent roofs 12c and 12d.
[0022]
Further, an intake valve 21 and an exhaust valve 22 are respectively provided in the intake port 16 and the exhaust port 17. The intake valve 21 is driven by the intake cam 19, and the exhaust valve 22 is driven by the exhaust cam 20. As shown in FIG. 1, the intake port has a straight shape and extends in parallel with the extension line LEX of the exhaust side pent roof 12d, or is inclined upward at an acute angle γ with respect to the extension line LEX. The acute angle γ is preferably in the range of 0 to 15 degrees. Further, the intake port 16 has an inclination angle θ (preferably in the range of 0 to 20 degrees) with respect to the vertical axis of the cylinder 11. The intake air is sucked through the intake port 16 configured in this way, flows into the combustion chamber 14 along the exhaust side pent roof surface 12d, and flows in a counterclockwise direction in the combustion chamber 14 as shown in FIG. Occur.
[0023]
Further, in this embodiment, the center line of the injector 15 indicated by the straight line B with respect to the perpendicular of the cylinder 11 is inclined at an inclination angle α (counterclockwise in the drawing) in order to obtain more effective fuel injection. Inclined toward the exhaust port 17.
[0024]
A curved cavity 13 b is formed on the top surface 13 a of the piston 13. The cavity 13b is formed in a shape and position that guides the tumble flow along the curved surface and smoothly winds the tumble flow toward the intake side pent roof 12c. As indicated by the one-dot oblique line in FIG. 3, the cavity 13 b is disposed at a position slightly offset toward the exhaust port 17, just below the injector 15.
[0025]
The electrode 23a of the spark plug 23 protrudes between the intake ports 16 of the intake side pent roof 12c so as to hit the tumble flow reflected by the cavity 13b and to be exposed to fuel spray when the fuel is injected. Yes.
[0026]
In general, there is a technical term called tumble ratio to express the strength of the tumble flow numerically. The tumble ratio is the amount of rotation of intake air per crankshaft rotation, and is determined by various factors such as the inclination angle of the intake port 16, the shape of the combustion chamber 14, the shape of the piston 13, and the like. In this embodiment, the tumble ratio is mainly determined by the inclination angle of the suction port 16, the position of the cavity 13b of the piston 13, and the curvature. Experiments have found that a tumble ratio in the range of 0.5 to 1.7 produces the most desirable results. When the tumble ratio is 0.5 or less, the tumble flow is attenuated before the compression stroke, and the formation of the air-fuel mixture fails. On the other hand, when the tumble ratio is 1.7 or more, the tumble flow is strong, the intake air that has been wound up from the cavity 13b of the piston 13 spreads toward the cylinder wall, and as a result, the injected fuel spray is scattered tumble. Due to the flow, the combustible mixture is not formed around the electrode 23 a of the spark plug 23. Therefore, the tumble ratio is desirably set in the range of 0.5 to 1.7.
[0027]
Furthermore, experiments have shown that a combination of an inclination angle α of 20 ° to −5 ° and an acute angle γ of 0 ° to 15 ° has the most desirable effect on the formation of a tumble flow. Furthermore, for the size and position of the cavity 13b, it has been found that the most desirable result is obtained when its diameter d (millimeter) is
d = D × 0.5−k
Here, D is the diameter (millimeter) of the piston, and k is a constant in the range of 0 to 5. As the depth and the offset amount from the cylinder axis, values in the range of 5 to 10, 0 to 5 millimeters are used, respectively.
[0028]
Next, the operation of the combustion chamber thus formed will be described.
In stratified combustion at an extremely low load, the engine is operated with BITI control, and reliable combustion is obtained. In this case, the best fuel injection timing is set near the ignition timing, and the fuel spray itself creates an air-fuel mixture near the electrode 23a of the spark plug 23, and this air-fuel mixture is ignited at the ignition timing. At an extremely low load, the gas flow is very slow, so that the air-fuel mixture is not affected by the shape of the piston cavity 13b.
[0029]
Further, in the BITE control corresponding to the constant speed running (R / L load), as shown in FIG. 8, the injector finishes the injection earlier than the BITI control. For this reason, the fuel spray in the latter stage of injection collides with the piston cavity 13b, and the flow of the fuel spray is wound up from there. That is, the combustible air-fuel mixture is formed around the electrode 13b of the spark plug 13 as shown in FIG. The dashed-dotted line b in FIG. 8 has shown the ignitability of the fuel injected at the same time as the case of the flat surface piston (refer FIG. 15). In the case of a flat surface piston, the fuel spray diffuses in the cylinder bore direction without being rolled up, so that no combustible mixture is formed around the electrode 23a of the spark plug 23. Therefore, the BITE control in this case is not performed because combustion deteriorates.
[0030]
Furthermore, in the BITE control at the time of acceleration load, as shown in FIG. 8, the fuel injection end timing is further advanced. In this case, the early injection timing promotes the diffusion or vaporization of the fuel spray. FIG. 6 shows an example of a combustion chamber in which the air-fuel mixture lies on the entire surface of the piston cavity 13b. When a tumble flow is applied in this state, these air-fuel mixtures roll up toward the electrode 23a of the spark plug 23, and a combustible air-fuel mixture is formed around the electrode 23b when just ignited. That is, as shown in FIG. 8, BITE control is possible even when ignition corresponding to acceleration is performed early. In the present embodiment, combustion is reliably maintained in a wide range from the retarded misfire limit (a) to the advanced misfire limit (d). The misfire limit (a) is a limit line, and the left side of the limit line is misfire caused by bringing the injection timing close to the ignition timing, that is, misfire caused by cutting the discharge path of the spark plug 23 by fuel spray. The range that causes
[0031]
FIG. 10 is a comparison data of combustion or exhaust gas characteristics between a piston having a flat top surface and a piston having a curved cavity.
[0032]
As can be understood from the comparison data, in the case of a piston having a curved cavity, even if the fuel injection end timing is set to the advance side, combustion is not adversely affected unless it is advanced considerably. In this case, the fuel injection timing can be set in a wide range. On the other hand, in the case of a piston with a flat top surface, if the fuel injection end timing is set to the advance side, an air-fuel mixture is not formed around the electrode 23a of the spark plug 23, causing bad combustion or misfire. Accordingly, the selectable range of the fuel injection end timing in this case is narrow.
[0033]
Referring to FIG. 11, these diagrams show the difference in combustion or exhaust gas characteristics with respect to tumble flow rotation direction and tumble ratio.
[0034]
Comparing the rotation direction of the present embodiment and the reverse rotation thereof, the tumble flow having the reverse rotation direction is inferior in terms of ignitability because the fuel spray is wound up in the opposite direction to the electrode of the spark plug. Proved. This tendency becomes more prominent as the fuel injection becomes earlier. For the influence of the tumble ratio, it has been proved that there exists a specific optimum value for the tumble ratio. According to experiments, it has been proved that the optimum value of the tumble ratio is 1.0 in the shape of the combustion chamber and the piston used in the present embodiment. Furthermore, it has been proved that reliable ignition can be obtained in the tumble ratio range of 0.5 to 1.7. That is, if the tumble ratio is 0.5 or less, the tumble flow is attenuated before reaching the compression stroke and is not used to form the air-fuel mixture. Furthermore, if the tumble ratio is 2.0 or more, the fuel spray is diffused because the tumble flow is strong, and as a result, a combustible mixture is not formed around the electrode of the spark plug.
[0035]
FIG. 9 shows the range of the operable air-fuel ratio with respect to the fuel injection timing when the BITE control is performed, with hatched portions. The air-fuel ratio range and fuel injection end timing within each operable range are determined by various limits such as cutting of the discharge path by fuel spray, generation of soot, combustion fluctuation, and the like. As can be seen from this figure, the BITE control extends from the stratified combustion to the uniform combustion range without adversely affecting the ignitability and combustibility of the engine by the air-fuel ratio in the operable range and the fuel injection end timing. Is maintained, and the air-fuel ratio can be continuously changed.
[0036]
FIG. 12 shows a second embodiment of the present invention.
In this second embodiment, the ignition plug 23 is rearranged from the intake port 16 side to the exhaust port 17 side, and its electrode 23 a projects into the combustion chamber 14 from between the two exhaust valves 22. In this case, since the inclination angle θ (clockwise in the drawing) of the intake port 16 with respect to the cylinder axis is designed to be narrower than the first embodiment, the tumble flow is in the opposite direction to the first embodiment, that is, this drawing. Wake up clockwise as shown above. The inclination angle θ is preferably set in the range of 0 to 20 degrees. That is, the air flow flowing into the combustion chamber 14 from the intake port 16 first collides with the top surface 13 a of the piston 13, and then a tumble flow is generated by the piston cavity 13 b of the piston 13. The tumble flow winds up from the piston cavity 13b toward the exhaust side pent roof surface 12d. The fuel spray injected from the injector 15 collides with the tumble flow and forms an air-fuel mixture there. In this embodiment, the injector is slightly inclined toward the intake port 16 by the inclination angle α so as to obtain a more effective fuel spray. In this embodiment, the inclination angle α of the injector 15 is preferably in the range of 0 to 20 degrees. In this way, a combustible mixture is formed around the electrode 23a of the spark plug 23.
[0037]
The first embodiment has an advantage that the diameter of the intake valve can be increased by disposing the spark plug 23 on the exhaust port side. Also in this embodiment, it is desirable to set the tumble ratio to a value in the range of 0.5 to 1.7.
[0038]
Although preferred embodiments of the present invention have been disclosed herein, these disclosures are merely examples, and various changes and modifications can be made without exceeding the scope of the invention.
[0039]
【The invention's effect】
As described above, according to the first embodiment of the present invention, the intake air guided into the combustion chamber is carried along the pent roof surface on the exhaust port side and after colliding with the curved piston cavity on the upper surface of the piston. The tumble flow is wound up near the electrode of the spark plug. On the other hand, according to the second embodiment, the intake air is guided into the combustion chamber, and after directly colliding with the curved piston cavity, the tumble flow is wound up near the electrode of the spark plug. When the injection timing is relatively late, that is, when it is relatively close to the ignition timing (stratified combustion region), the air-fuel mixture is formed in the vicinity of the spark plug electrode by the sprayed fuel itself and ignited by the spark plug. When the injection timing is relatively early, that is, when it is relatively far from the ignition timing (stratified combustion region), the sprayed fuel is reflected by the piston cavity, and the reflected fuel spray is mixed around the electrode of the spark plug. Form. Thereafter, the air-fuel mixture is ignited at a predetermined ignition timing. If the injection timing is earlier (in this region, stratified combustion occurs first, followed by uniform combustion), the sprayed fuel is trapped in the piston cavity, and this trapped fuel mixes with the rising tumble flow. The air-fuel mixture reaches the vicinity of the spark plug electrode. Thereafter, the air-fuel mixture is ignited at a predetermined ignition timing. Switching from stratified combustion to uniform combustion is made continuously. Thus, stable ignitability and stable combustion performance can be obtained in all operating states of the engine. This stable combustion results in suppression of exhaust emissions such as HC, CO, NOx, etc. exceeding the allowable range and improvement in fuel efficiency, allows stratified combustion to be expanded to a high load range, and switches from stratified combustion to uniform combustion. Smooth and good drivability can be provided.
[0040]
Furthermore, by setting the rotational speed of the tumble flow per engine revolution to 0.5 to 1.7, the tumble flow during the compression stroke is not attenuated and the fuel is not diffused, and the combustible mixture is ignited. It is formed around the electrode of the plug.
[0041]
According to the first embodiment, the arrows in FIGS. 1, 2 and 7 indicate the air flow guided from the upper surfaces of the intake pipe 16 and the combustion chamber 14 to the cavity 13b of the piston 13, and the tumble flow is generated counterclockwise. . Therefore, the inflow air is effectively mixed with the fuel injected from above.
[0042]
According to the second embodiment, the arrows in FIG. 12 indicate the air that has flowed into the combustion chamber, that is, into the cavity 13 b of the piston 13. The tumble flow occurs clockwise. Therefore, the inflowing air is effectively mixed with the fuel injected from above, and is ignited efficiently by the electrode 23a of the spark plug 23 for optimal combustion.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a combustion chamber of a direct injection spark ignition engine in a first embodiment of the present invention. FIG. 2 is a side view showing the structure of the combustion chamber of the first embodiment of the present invention. 3 is a plan view of the combustion chamber according to the first embodiment of the present invention. FIG. 4 is a side view showing fuel spray behavior immediately before the ignition timing in the combustion chamber of FIG. 1. FIG. FIG. 6 is a side view showing the behavior of the combustion spray colliding with the cavity. FIG. 6 is a side view showing the fuel spray behavior when there is no tumble flow during acceleration in the combustion chamber of FIG. Side view showing fuel spray behavior when tumble flow occurs during acceleration [Fig. 8] Characteristic diagram showing relationship between combustion stability and injection timing [Fig. 9] Characteristic showing relationship between operable range and optimum injection timing [Fig. 10] Flat top piston and curved cavity Comparison data of combustion or exhaust gas characteristics with a piston having a cylinder [Fig. 11] Comparison data showing difference in characteristics of combustion or exhaust gas with respect to tumble flow rotation direction and tumble ratio [Fig. 12] Second embodiment of the present invention FIG. 13 is a characteristic diagram showing the relationship between the fuel injection end timing and the fuel injection amount in the prior art. FIG. 14 is a characteristic diagram showing the relationship between the emission amount and the fuel injection timing. 15] Schematic diagram showing the combustion chamber of a prior art direct injection spark ignition engine
12b Combustion chamber top 12c Intake side pent roof surface 12d Exhaust side pent roof surface 13a Piston top surface 13b Cavity 14 Combustion chamber 15 Injector 16 Intake port 23 Spark plug 23a Electrode

Claims (7)

In the combustion chamber structure of an in-cylinder direct injection spark ignition engine that generates a tumble flow in the intake air supplied through the intake port that opens to the roof of the combustion chamber,
Between the intake port and the exhaust port that are opened in the roof of the combustion chamber, an injector that is inclined by a first inclination angle toward the exhaust port side with respect to the axis of the cylinder is disposed,
Inclined to the exhaust port side roof or parallel to the exhaust port side roof so that the intake port forms an intake tumble flow along the exhaust port side roof,
A curved piston cavity is formed on the top surface of the piston to reflect the fuel spray injected from the injector together with the intake tumble flow toward the roof on the intake port side,
A spark plug is disposed on the roof on the intake port side,
An in-cylinder direct injection spark ignition engine characterized in that an electrode of the spark plug is located in the vicinity of the injection hole of the injector and at an outflow position of the fuel spray reflected by the intake tumble flow and the piston cavity. Combustion chamber structure. In the combustion chamber structure of an in-cylinder direct injection spark ignition engine that generates a tumble flow in the intake air supplied through the intake port that opens to the roof of the combustion chamber,
Between the intake port and the exhaust port that are opened in the roof of the combustion chamber, an injector that is inclined by a first inclination angle toward the exhaust port side with respect to the axis of the cylinder is disposed,
The intake port is inclined by a second inclination angle with respect to the axis of the cylinder so that the intake air directly collides with the piston to form an intake tumble flow;
A curved piston cavity is formed on the top surface of the piston to reflect the fuel spray injected from the injector along with the intake tumble flow toward the roof on the exhaust port side,
A spark plug is disposed on the roof on the intake port side,
An in-cylinder direct injection spark ignition engine characterized in that an electrode of the spark plug is located in the vicinity of the injection hole of the injector and at an outflow position of the fuel spray reflected by the intake tumble flow and the piston cavity. Combustion chamber structure.   The combustion chamber structure of a direct injection type spark ignition engine according to claim 1, wherein the first inclination angle is in the range of 0 to 20 °.   The combustion chamber structure of an in-cylinder direct injection spark ignition engine according to claim 2, wherein the first inclination angle is in the range of 0 to -20 °.   The in-cylinder straight according to claim 1 or 3, wherein the intake port is disposed at an acute angle including parallel to the roof on the exhaust port side, and the acute angle is in a range of 0 to 15 °. Combustion chamber structure of an injection spark ignition engine.   The combustion chamber structure of a direct injection type spark ignition engine according to claim 2 or 4, wherein the second inclination angle is in a range of 0 to 20 °.   The combustion chamber structure of a direct injection type spark ignition engine according to any one of claims 1 to 6, wherein the amount of rotation of the tumble flow per engine rotation is in the range of 0.5 to 1.7. .

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